Chlorinated synthetic rubber



.by weight of the rubber-like materials.

Patented July 31, 1945 Gaetmo F. DAlelio, rimm fllilnor to General Electric Company, a corporation oi.

New York No Drawing. Application December 10, 1941,

-, SerlalNmmAfl 4 Claims. (Cl. 280-845) no carbon tetrachloride. It is round to contain about 45 per cent by weight of chlorine. Another "Perbunan and -Perbunan Extra" synthetic I rubber-like materials, which are vulcanizable mixed polymers of 1,8-butadlene and acrylic acid nitrile, are described for example in Patent 1,973,000 Konrad et a1. Ordinarily commercial Perbunan contains from 20 to 30 per cent by weight of acrylic acid nitrile while the "Perbunan Extra has a higher acrylic acid nitrile content but generally not exceeding about 40 percent Perbunan is one of the most widely used substitutes for rubber. It resembles rubber in many of its physical and chemical properties and has been recognized and used as a substitute for rubber in many applications.

In the unvulcanized state, 1,3-butadieneacrylic acid nitrile mixed polymerizates are nonportion oi the mass also becomes brittle and non-rubbery, but rather brownish in color, and contains about 22 per cent by weight of chlorine. The major portion of the chlorinated mass is a very tough, rubbery product which is much stronger and more elastic than the original "Perbunan'. This rubbery product contains about 1.85 per cent by weight of chlorine.

As the above-mentioned brittle, non-rubbery chlorinated products result from over chlorination of the Perbunan primarily in those portions of the swollen mass in most direct contact with the chlorine gas, it is desirable that the chlorination oi the "Perbunan" should be controlled to result in the production of only the" touch. rubbery product. This may be done either elastic in that sheets or strips thereof do not return to their original form after being elongated or stretched to a substantial extent. Again, like unvulcanized crepe rubber, these mixed polymerizates are physically weak and tend to tear when stretched.

The present invention is based on my discovery that tough, strong, elastic products which have an extensibility of the order of 600% over the non-chlorinated starting material may be obtained by introducing up to 3 per-cent, preferablv from 1 to 2 per cent, by weight, of chlorine into the 1,3-butadiene-acrylic acid nitrile mixed polymers, particularly the Perbunan" synthetic rubbers.

Any of a number of ways may be used for chemically combining chlorine with the mixed polymerizate. swollen by the addition of any liquid swelling agent such as carbon tetrachloride, benzene,

toluene, ethylene dichloride, or the like which is tlon during the chlorination reaction or by controlling the amount of chlorine available for the reaction. For example, the chlorination reaction may be carried out in a closed chamber wherein the mass is being continually mixed or agitated bymeans of suitable mixing devices during the time the chlorine gas is being introduced. Alternatively, the degree or chlorination or the mixed polymerirate may be controlled by introducing a Preferably the mass is agitated vigorously during For example, the polymerizate is tight container and treated with chlorine gas at m a pressure or about 21 lnches'oi. mercury ior six days. Three chlorinated products are obtained. A white brittle non-rubbery mass forms on the and after the addition of the chlorine solution.

After the mixed polymerlzate has been chlorinated to the desired extent, the solvent is removed by drying the product to constant weight. The dried product softens sumciently under heat and pressure so that it can be molded to term articles or exceedingly high strength.

' The rubbery chlorinated product is sufllcien plastic to be worked'on rubber-rolls. It may be modified by the addition of fillers, l. e. carbon black, zinc oxide, the highly chlorinated mixed polsmeriaates mentioned hereinbetore, etc.. and/or vulcanizers, vulcanization accelerators andactivatoraetcqsuchasthoseusedinvub.

canlsing the unchlorinated mixed polymerizate. The modified or unmodified products may then bemhstitutedmrtheordinaiymixedpdymcrl topottheswollenmasswherethercislittleoru orwherevcraproducthavinggreaterstrength.

acrylic acid nitrile.

toughness, and elasticity is required. other modiiiers include various -'mina. "Perbunan or other natural or synthetic rubbers, which will lend their own properties to the modified products. 7 If desired, the plasticity and extmdability of I the chlorinated product may be improved by the addition of suitable softeners such as tricresyl phosphate, dibenzyl ether, certain alkyd resins or the-like.

Although I have described my invention with particular reference to "Perbunan it is to be understood that it is also applicable to the "Perbutadiene and acrylic nitrile containing from 1 to 3- percent by weight of chlorine, the said polymerizate' containing from 20 to 40 per cent by weight of acrylic nitrile.

2. A tough. strong, elastic, chlorinated mixed polymerizate of LS-butadiene and acrylic nitrile containing from 1 to 2 per cent'chlorine chemically combined therewith, the said polymerizate comprising from 20 to 30 per cent by weight of acrylicnitrile.

- 3. The vulcanized product or claim 1.

4. A tough, strong, elastic chlorinated mixed polymerizate of 1,3-butadiene and acrylic acid nitrile containing about 1.85 per cent chlorine, the acrylic acid nitrile comprising from 20 to 30 per cent by weight 01 said mixed polymerizate.

GAEI'ANO F. DALELIO. 

